First Drive: 2010 Mercedes-Benz ML450 Hybrid

Mercedes-Benz today unveiled its latest effort to reduce the fuel consumption of its large luxury vehicles with the launch of the 2010 ML450 Hybrid. This new mdoel of the ML sport utility, built in Tuscaloosa, Alabama, is fitted with the Two-Mode Hybrid system jointly developed by General Motors, Daimler, Chrysler, and BMW.

The ML450 Hybrid hasn’t been priced yet, and Benz is likely sweater the numbers to work out how to sell it at a profit. The Benz uses a larger 2.4-kilowatt-hour nickel-metal-hydride battery pack than other Two-Mode vehicles—half again as large as the Cadillac Escalade Hybrid pack—along with liquid cooling to keep it at the right temperature. Those components aren’t cheap, but Benz also isn’t commenting on how many it expects to sell.

The Two-Mode Hybrid transmission packs a pair of electrical motors and several gear-sets into the same space as a conventional automatic transmission. It can operate solely on electric power at lower speeds, but unlike smaller hybrid systems like those in the Toyota Prius, it also offers electric assist at highway speeds.

A 45-minute test drive in the ML450 Hybrid showed that Benz has done its homework, with very little drivetrain noise and the customary levels of luxury. The regenerative braking blends seamlessly into the friction brakes, with imperceptible engine starts and stops. Ignoring the power split display on the center stack and the charge meter next to the speedometer, the only sign of the hybrid under the hood was an occasional disconnect between engine noise and road speed.

For those drivers disconcerted by that CVT-like experience, Benz offers a “Shift” mode that changes the control software to imitate the behavior of an engine linked to an eight-speed automatic transmission. It costs about 3 percent of the gas mileage, but drivers using “S” mode may literally never know they’re driving a hybrid.

The Mercedes-Benz ML series will now become the only one sold in North America that offers standard gasoline engines (15 / 24 mpg for the 3.5-liter), a diesel option (18 /24 mpg for the 3.0-liter BlueTec diesel) and a hybrid system. May the best green system win.--By John Voelcker